Olympus for
the Concorde
POWERPLANT DEVELOPMENT REVIEWED
THE news that the Olympus 593 B engine for the Concordeattained 33,OOOlb dry thrust six weeks after its initial run(as reported in Flight for January 6, page 3) came just
over three years after the Anglo-French Treaty of Collabora-
tion signed in November 1962. For Bristol Siddeley and
SNECMA the three years have been a period of great activity.
When the Concorde was first projected, the engine proposed
was a developed version of the military Olympus 320 for the
TSR.2, modified for civil operation. Like the earlier series of
military Olympus engines, the 320 was a two-spool engine,
each compressor driven by a separate turbine, with a cannular
combustion chamber.
The principal differences between the Olympus 320 and the
engine for Concorde were calculated to increase the dry thrust
rating from about 20,0C01b to 29,3001b while at the same time
reducing internal operating stresses to a level where component
life would permit the necessary time between overhaul for
civil operation. Air mass flow was increased by 20 per cent and
the same pressure ratio maintained by removing a blade stage
from the rear of the high-pressure compressor and adding
another to the front of the low-pressure compressor. Turbine
entry temperature was increased by the substitution of a cooled
high-pressure turbine stator and rotor. With these and other
detail modifications made, the design of the first civil Olympus
engine, the Olympus 593D was frozen.
Within 12 months of the go-ahead being given to the Con-
corde project, a major redesign of the aircraft was carried
through to improve operating range. One feature of this opera-
tion was an increase in take-off weight which demanded 12 per
cent greater thrust from the engines.
While the required thrust increase could be contained within
the development envelope of the existing engine, Bristol Sid-
deley felt strongly that such a move so early in its history
wrote-off too large a part of the long-term development poten-
tial. As a result, it was decided to redesign the Olympus 593
around new compressors and turbines in order to meet the in-
creased thrust. This was possible, because the redesign of the
Concorde airframe required a revised, and longer, time-scale,
putting back first flight by about two years and the in-service
date by roughly 12 months.
On January 1, 1964, the specification of the new engine was
finalised. To distinguish it from the original Concorde engine
it was designated Olympus 593B—B for "big"—while the
earlier, smaller, engine became the Olympus 593D, the D stand-
ing for "derivation." Since six sets of components for the
Olympus 593D were already approaching completion, the revised
FUGHT International, 13 January
programme called for two engines of this standard to be com-
pleted and tested to provide early running experience.
At the same time, material was ordered for 15 bench and
two flight engines of the new Olympus 593B standard.
The first 593D engine ran in July 1964, followed by the
second in September of the same year. To date, they have
together run for about 180hr. Testing has logically concentrated
on specific areas where results can be read across directly to
the Olympus 593B. A major part has concerned test equipment
development, including heated intakes, which allow supersonic
operating conditions to be simulated on a test bed at sea level.
As a result, considerable work has already been cleared which
otherwise would have had to proceed parallel with early testing
of the Olympus 593B.
With only a convergent nozzle fitted to the engine, 28,0001b
thrust was achieved at full air mass flow and turbine entry
temperature on a number of occasions. Since the combustion
chambers on the Olympus 593D and 593B are similar, and both
engines have cooled first-stage turbines, tests covering these
aspects have proved of very real value. For example, design
of the cooled first stage turbine stator blades has been improved
as a result of 593D tests.
Jetpipe and nozzle components designed and built by
SNECMA have been tested on the 593D and also on Olympus
301 engines, both in Britain and France. A jetpipe, primary
nozzle and an afterburner to the 593B standard have been run.
With the acceptance test of the first 593B completed, and a
further five engines due for test before the middle of this year,
the 593D will shortly be phased out. They will be used for the
first stages of a destructive test programme, involving such
items as ice ingestion, bird strike and overspeed tests.
At the moment one 593D is being used for testing the air
dumping system which will eliminate the effect of shock-wave?
forming in an air intake when the engine is in a stalled con-
dition. A further engine, shortly to begin trials, will be fitted
with a weakened low-pressure driveshaft. It will be run until
the shaft distorts to test a strain-gauge device which will cut
off fuel in sufficient time to avoid overspeeding of the 1-p tur-
bine in the event of driveshaft failure. Without such a precau-
tionary device the turbine could overspeed by as much as 160
per cent—by which time the blades would be parting company
with the turbine ring—as the fuel system is driven from the
h-p turbine and the lag in sensing the failure, although only a
fraction of a second, would be disastrous.
Larger Dimensions
The Olympus 593B is physically larger than the 593D. The
diameter of the intake is about 2.5in greater and that of the
turbine casing around 2in greater, and the engine is about lOin
longer.
Mass flow of the 593B is over 4001b/sec. When the engine
enters service the dry thrust rating will be 32,8001b, increased to
35,0001b with reheat. This engine is designated Olympus 593B
Stage 0 and is a de-rated version -of the full production Stage I
engine, designed for 35,OCOlb dry thrust.
Ds-rating has been introduced to enable flight experience to
be gained at moderate operating conditions. Two years after
the Concorde enters service the Stage 1 engine will be made
available at slightly increased compressor speed, and hence
mass flow, and with a higher turbine entry temperature. In this
way both performance and overhaul life will be developed
side by side to give operators the best of both worlds.
The Olympus 593B again follows the classic Olympus layout
of a twin-spool compressor, each spool with seven stages, driven
by independent turbines, and a cannular combustion system.
Casings of both compressor elements are in steel, with all discs
and blades except for the last few high-pressure stages manu-
factured from titanium alloys. To meet th« high cruise operating
temperatures in the engine, the rear stages of the h-p compressor
are in Nimonic 90.
Drives for all aircraft and engine accessories are taken from
the front of the h-p compressor driveshaft through the inter-
mediate casing linking the two compressor spools. The engine
and aircraft accessory gearboxes have separate drives, each
engine providing auxiliary power for two hydraulic pumps, a
constant-speed drive unit and its associated electrical generator,
and for the engine accessories.